1. Field of the Invention
The present invention relates to a magnetic head used for rotary head of a video tape recorder or the like and a head apparatus assembled by using the magnetic head.
2. Description of the Related Art
As shown in FIGS. 11(a) and 11(b) the conventional structure of a magnetic head 1 used for a video tape recorder (VTR) comprises a head chip 2 consisting of magnetic substances bonded to a brass head base 3, and a wire wound around the head chip. A terminal strip 4 is bonded to a surface of the head base 3, and an end of a winding member 5 is soldered to the terminal strip 4. The magnetic head 1 is assembled in this way and fixed to a surface of an upper drum 6, which forms one of the rotary drums, with a screw 7 as shown in FIG. 11(c). The fixed condition is shown in FIG. 11 (d). FIGS. 11 (c) and (d) illustrate rotary drums with two heads. The upper drum 6, assembled as shown in FIG. 11(d), is fitted into a lower drum 8, a rotary portion being formed in the center of the lower drum 8 as shown in FIG. 11(e). A rotary transformer 9 is composed of a fixed side core 9a and a rotary side core 9b disposed under the rotary portion. Wires are wound around each core 9a and 9b. The side of the magnetic head 1 and a side of a recording and/or reproducing circuit (not illustrated) are electro-magnetically coupled through the rotary transformer 9.
FIG. 12 shows the coupled condition of the upper drum 6 and the lower drum 8. In FIG. 12, reference numeral 10 represents a fixed portion, while numberal 11 represents a rotary portion. The upper drum 6 on the side of the rotary portion 11 is fixed to the tip of a rotary axis 12 and rotated by rotation driving means (not illustrated). Also, a printing base 13 is fixed on the upper surface of the upper drum 6. A coil on the rotary side of the rotary transformer 9 is connected to the printing base 13 with a wire 14.
Individual brass head base 3 is produced by die formation in the above mentioned conventional magnetic head 1. When the magnetic head 1 is assembled, a separate head chip 2 is combined with the head base 3. Therefore, the brass head base 3 also serves as a jig during the manufacturing processes, which include bonding the head chip 2 to the head base 3, winding wires, molding, and a curvature finishing of a chip sliding surface. Then, when the single magnetic head 1 is carried, a special housing case is needed so that it is not damaged. It is recognized that video tape recorder are now being integrated with a camera therefore, there exists a need to make the video tape recorders smaller and lighter so that they can be easily transported. Also, it has become necessary for the head base used for a small-sized video tape recorder to be made smaller lighter as a matters of course. There is also a need, however, for the head base structure to be manufactured with high precision and processability.
For example, since a 8 mm VTR integrated with a camera has a small diameter of a rotary drum cylinder typically 30 mm and event less, the size of the head base should be smaller as a matter of course.
Since the brass base has a relatively high thermal conductivity coefficient, adjacent solder melts because of the heat transferred therethrough from, for example, a glass epoxy base bonded to the brass base, when an end of a wire is soldered to a terminal strip. Thus, there is a problem in that a soldering iron cannot be pressed for a long enough time for effective soldering.
Also, when a flying erase head, used for erasing a recording on a video tape and eliminating noise (called rainbow noise), is fitted to a rotary drum, a dummy base of the same weight must be positioned on a diagonal line in order to keep the weight balanced when the rotary drum is rotated.
While, instead of metal brass, ceramic material and plastic material have been investigated as a material for the base board; however, ceramic material is hard to be processed and has a high cost, while plastic material has weak weatherability and mechanical strength and change has a large thermal expansion coefficient 3 and poor heat stability. As a result, although plastic material is light, material it can not take the place of brass. Also, generally, a chip and base board require grounding to prevent electrification in the head chip. For this additional reason, ceramic and plastic materials cannot be used.
Further, since it is difficult for bonding agents to penetrate through conventional base board materials when the head chip is bonded to the head base, the bonding strength of the chip is weak.
As explained above, due to the base board materials, a conventional magnetic head has many problems associated its manufacturing processes, chip bonding strength, portability, and solderability. There is also a problem in that the magnetic head is unsuitable for miniaturization and reducing the weight thereof.